Changing analog TV to digital flatscreen

Like other said, you're going to have to do some modification and use the type of mount that is most suitable. You're going from a deep hole that is designed to hold a very deep TV to a type of setup that uses a flat TV with very little depth. I would probably go with some sort of swing out mount fastened to a built-out area. Most of the newer generation flatscreens are very light so this gives you a lot of options.